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Nanoindentation Study Of Corrosion-Induced Grain Boundary Degradation In A Pipeline Steel, Denizhan Yavas, Pratyush Mishra, Abdullah Alshehri, Pranav Shrotriya, Kurt R. Hebert, Ashraf F. Bastawros 2018 Iowa State University

Nanoindentation Study Of Corrosion-Induced Grain Boundary Degradation In A Pipeline Steel, Denizhan Yavas, Pratyush Mishra, Abdullah Alshehri, Pranav Shrotriya, Kurt R. Hebert, Ashraf F. Bastawros

Aerospace Engineering Publications

High-strength low-alloy steels used for oil and gas pipelines are vulnerable to intergranular stress corrosion cracking in moderately alkaline soils. The mechanism of corrosion-induced embrittlement under such conditions is not yet understood. Nanoindentation was used to detect localized degradation of mechanical properties near internal grain boundaries of X-70 steel undergoing intergranular corrosion at active dissolution potentials at pH 8.2. The measurements identified a one-micron thick mechanically-degraded layer with 25% reduced hardness near corroded grain boundaries. It is suggested that the corrosion process may introduce an active softening agent, possibly non-equilibrium lattice vacancies generated by oxidation.


Model-Assisted Approach For Probability Of Detection (Pod) In High-Temperature Ultrasonic Nde Using Low-Temperature Signals, Prathamesh N. Bilgunde, Leonard J. Bond 2018 Iowa State University

Model-Assisted Approach For Probability Of Detection (Pod) In High-Temperature Ultrasonic Nde Using Low-Temperature Signals, Prathamesh N. Bilgunde, Leonard J. Bond

Aerospace Engineering Publications

Advanced piezoelectric-based ultrasonic transducers offer the potential for in-coolant nondestructive testing (NDT) measurements at high temperatures (HTs), including during hot standby (~260°C) for liquid-sodium–cooled advanced small modular reactors. The reliability of the NDT measurements is typically quantified by the probability of detection (POD) measured at the corresponding temperature. Obtaining such data in liquid sodium is challenging. Using a model-assisted POD approach, a transfer function is reported that enables data obtained on low carbon steel specimens at room temperature to give an estimated POD at an HT. A primary source of the difference in POD between room temperature and ...


Assessment And Comparison Of Aviation Manufacturing Industries Throughout Mexico And Brazil, Omar E. Morsi, Kelly A. Whealan-George, Aaron D. Clevenger 2018 Embry-Riddle Aeronautical University

Assessment And Comparison Of Aviation Manufacturing Industries Throughout Mexico And Brazil, Omar E. Morsi, Kelly A. Whealan-George, Aaron D. Clevenger

International Journal of Aviation, Aeronautics, and Aerospace

This literature review serves to provide insight and understanding in regards to the evolving aviation manufacturing industry throughout the globe and more specifically, Mexico and Brazil. Increased demand for aircraft units both in the commercial and private sectors have led to unprecedented expansions in aircraft manufacturing across the industry. In order to illuminate certain potentials and current growth levels of such industries, this review will delve into an array of information and specifications in regards to economic, political, and cultural influences throughout both Mexican and Brazilian markets respectively. In conclusion, the review will identify the transformation of an aviation manufacturing ...


Numerical Analysis Of Aerodynamic Noise Mitigation Via Leading Edge Serrations For A Rod–Airfoil Configuration, Bharat Raj Agrawal, Anupam Sharma 2018 Iowa State University

Numerical Analysis Of Aerodynamic Noise Mitigation Via Leading Edge Serrations For A Rod–Airfoil Configuration, Bharat Raj Agrawal, Anupam Sharma

Anupam Sharma

Noise produced by aerodynamic interaction between a circular cylinder (rod) and an airfoil in a tandem arrangement is investigated numerically using incompressible large eddy simulations. Quasi-periodic shedding from the rod and the resulting wake impinges on the airfoil to produce unsteady loads on the two geometries. These unsteady loads act as sources of aerodynamic sound and the sound radiates to the far-field with a dipole directivity. The airfoil is set at zero angle of attack for the simulations and the Reynolds number based on the rod diameter is Red = 48 K. Comparisons with experimental measurements are made for (a) mean ...


Nanoscale Multiphase Phase Field Approach For Stress- And Temperature-Induced Martensitic Phase Transformations With Interfacial Stresses At Finite Strains, Anup Basak, Valery I. Levitas 2018 Iowa State University

Nanoscale Multiphase Phase Field Approach For Stress- And Temperature-Induced Martensitic Phase Transformations With Interfacial Stresses At Finite Strains, Anup Basak, Valery I. Levitas

Aerospace Engineering Publications

A thermodynamically consistent, novel multiphase phase field approach for stress- and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic ...


Investigation Of 2195 And 2219 Post Weld Heat Treatments For Additive Friction Stir Lap Welds, Matthew Champagne 2017 University of New Orleans

Investigation Of 2195 And 2219 Post Weld Heat Treatments For Additive Friction Stir Lap Welds, Matthew Champagne

University of New Orleans Theses and Dissertations

To evaluate potential uses for friction stir welding in additive manufacturing, two separate parts were fabricated, one of 2195-T84 and the other 2219-T87, utilizing fixed pin techniques and additive lap welds. The parts were cut into samples, artificially aged and subjected to Rockwell hardness (HRB), Vickers hardness, micrographic photography, and metallographic imaging on both pre- and post- heat treatment. Additionally, tensile testing was performed on the heat-treated samples. A comparisons of test results showed a minimal increase in the yield strength of the 2195-T84 samples compared to as-welded tensile results obtained from a previous project. The ultimate tensile strength was ...


Rethinking The Design Of Low-Cost Point-Of-Care Diagnostic Devices, Faith W. Kimani, Samuel M. Mwangi, Benjamin J. Kwasa, Abdi M. Kusow, Benjamin K. Ngugi, Jiahao Chen, Xinyu Liu, Rebecca Cademartiri, Martin M. Thuo 2017 Kiambu District Hospital

Rethinking The Design Of Low-Cost Point-Of-Care Diagnostic Devices, Faith W. Kimani, Samuel M. Mwangi, Benjamin J. Kwasa, Abdi M. Kusow, Benjamin K. Ngugi, Jiahao Chen, Xinyu Liu, Rebecca Cademartiri, Martin M. Thuo

Materials Science and Engineering Publications

Reducing the global diseases burden requires effective diagnosis and treatment. In the developing world, accurate diagnosis can be the most expensive and time-consuming aspect of health care. Healthcare cost can, however, be reduced by use of affordable rapid diagnostic tests (RDTs). In the developed world, low-cost RDTs are being developed in many research laboratories; however, they are not being equally adopted in the developing countries. This disconnect points to a gap in the design philosophy, where parameterization of design variables ignores the most critical component of the system, the point-of-use stakeholders (e.g., doctors, nurses and patients). Herein, we demonstrated ...


Comparison Of Acoustoelastic Lamb Wave Propagation In Stressed Plates For Different Measurement Orientations, Ning Pei, Leonard J. Bond 2017 Iowa State University

Comparison Of Acoustoelastic Lamb Wave Propagation In Stressed Plates For Different Measurement Orientations, Ning Pei, Leonard J. Bond

Aerospace Engineering Publications

High order Lamb waves are investigated for the effects of stress on both symmetrical and anti-symmetrical modes in an aluminum plate for wave propagation and load parallel. Data are compared with those for the case of load and measurement axis perpendicular. It is the S1 mode which exhibits significantly higher sensitivity to stress than other Lamb modes. For aluminum the use of the S1 mode for stress measurement is found to be about six times more sensitive, than bulk waves, for the load-measurement axes parallel case and this compares with about ten times for the case of load-measurement axes perpendicular.


The Shaping Of Things That Are: How Airplane Windows Took Their Shape, Morgan Lopez 2017 Embry-Riddle Aeronautical University

The Shaping Of Things That Are: How Airplane Windows Took Their Shape, Morgan Lopez

Student Works

Have you ever wondered why your airplane's windows are rounded? It is not for aesthetic appeal.

The first commercial jetliner windows' sole purpose was appearance; a squared window afforded an impressive view of the earth, but the view was not without consequence.


Electron Yield Measurements Of High-Yield, Low-Conductivity Dielectric Materials, Justin Christensen 2017 Utah State University

Electron Yield Measurements Of High-Yield, Low-Conductivity Dielectric Materials, Justin Christensen

All Graduate Theses and Dissertations

Materials exposed to the space plasma environment acquire electric charge, which can have harmful effects if it leads to arcing or electrostatic breakdown of important spacecraft components. In fact, spacecraft charging is the leading environmentally induced cause of spacecraft anomalies. This study focuses on measuring electron yield, a property of materials that describes how many electrons are ejected from a material under energetic electron bombardment, which can vary depending on the energy of incident electrons. Intrinsic electron yield is defined as the average number of electrons emitted per incident electron from an electrically neutral material. The specific aim of this ...


Pressure Self-Focusing Effect And Novel Methods For Increasing The Maximum Pressure In Traditional And Rotational Diamond Anvil Cells, Biao Feng, Valery I. Levitas 2017 Iowa State University

Pressure Self-Focusing Effect And Novel Methods For Increasing The Maximum Pressure In Traditional And Rotational Diamond Anvil Cells, Biao Feng, Valery I. Levitas

Aerospace Engineering Publications

The main principles of producing a region near the center of a sample, compressed in a diamond anvil cell (DAC), with a very high pressure gradient and, consequently, with high pressure are predicted theoretically. The revealed phenomenon of generating extremely high pressure gradient is called the pressure self-focusing effect. Initial analytical predictions utilized generalization of a simplified equilibrium equation. Then, the results are refined using our recent advanced model for elastoplastic material under high pressures in finite element method (FEM) simulations. The main points in producing the pressure self-focusing effect are to use beveled anvils and reach a very thin ...


Structural Behavior Of Inflatable, Reinforced, Braided, Tubular Members, Joshua Clapp 2017 University of Maine

Structural Behavior Of Inflatable, Reinforced, Braided, Tubular Members, Joshua Clapp

Electronic Theses and Dissertations

The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) system being developed by the National Aeronautics and Space Administration (NASA) is an inflatable structure composed of multiple, concentric, pressurized tori, load straps, and a thermal protection system. The HIAD overcomes limitations inherent with the use of rigid decelerators since the deployed diameter is much larger than the packed size, which makes it an enabling technology for new opportunities in space exploration. The HIAD is designed to decelerate and protect spacecraft during atmospheric re-entry. The objective of this research was to improve understanding of structural behavior of HIAD components through material testing, structural testing ...


Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler 2017 Iowa State University

Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler

Nicola Bowler

This work investigates the electrothermal lifetime of a commonly used polyimide wire insulation material, Kapton®, through the use of thermogravimetry (TG) and breakdown voltage testing. From TG, an isoconversional model-free kinetic evaluation was used to obtain a relationship between the activation energies of degradation for Kapton as a function of weight loss. By relating the electrical life theory and the TG theory through the model defined by Toop (IEEE Trans. Dielectr. Electr. Insul. 1971, 6, 2), the electrothermal lifetime of Kapton has been calculated for conditions of 12 and 14.7 kV over a temperature range of 250–400°C ...


Hazard Assessment Of Meteoroid Impact For The Design Of Lunar Habitats, Herta Paola Montoya, Shirley Dyke, Julio A. Ramirez, Antonio Bobet, H. Jay Melosh, Daniel Gomez 2017 Purdue University

Hazard Assessment Of Meteoroid Impact For The Design Of Lunar Habitats, Herta Paola Montoya, Shirley Dyke, Julio A. Ramirez, Antonio Bobet, H. Jay Melosh, Daniel Gomez

The Summer Undergraduate Research Fellowship (SURF) Symposium

The design of self-sustaining lunar habitats is a challenge primarily due to the Moon’s lack of atmospheric protection and hazardous environment. To assure safe habitats that will lead to further lunar and space exploration, it is necessary to assess the different hazards faced on the Moon such as meteoroid impacts, extreme temperatures, and radiation. In particular, meteoroids pose a risk to lunar structures due to their high frequency of occurrence and hypervelocity impact. Continuous meteoroid impacts can harm structural elements and vital equipment compromising the well-being of lunar inhabitants. This study is focused on the hazard conceptualization and quantification ...


Using High Resolution Images To Investigate Fatigue Crack Initiation Of Alloys At The Microstructural Level, Michael P. Reinhold, Alberto Mello, Michael Sangid 2017 Purdue University

Using High Resolution Images To Investigate Fatigue Crack Initiation Of Alloys At The Microstructural Level, Michael P. Reinhold, Alberto Mello, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Microstructural features within a material dictate the material’s mechanical behavior and lead to localized strains as the sample is deformed. In order to further understand structural failure, an improved understanding of how microstructural features influence failure is necessary. Fatigue is one common mode of failure for aerospace applications, and a better understanding of the conditions of crack initiation can provide information that ultimately may increase longevity of aerospace systems. This paper investigates the hypothesis that fatigue crack initiation for a cyclically loaded sample is correlated to areas of higher localized strain. The experiment was conducted using a Ti-6Al-4V sample ...


Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark 2017 University of Arkansas, Fayetteville

Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark

Stephanie Clark

Recent advances within the field of cube satellite technology has allowed for the possible development of a maneuver that utilizes a satellite's Low Earth Orbit (LEO) and increased atmospheric density to effectively use lift and drag to implement a noncoplanar orbital maneuver. Noncoplanar maneuvers typically require large quantities of propellant due to the large delta-v that is required. However, similar maneuvers using perturbing forces require little or no propellant to create the delta-v required. This research reported here studied on the effects of lift on orbital changes, those of noncoplanar types in particular, for small satellites without orbital maneuvering ...


Meso-Scale Imaging Of Composite Materials, Robert J. Grandin, Joseph N. Gray 2017 Iowa State University

Meso-Scale Imaging Of Composite Materials, Robert J. Grandin, Joseph N. Gray

Robert Grandin

The performance of composite materials is controlled by the interaction between the individual components as well as the mechanical characteristics of the components themselves. Geometric structure on the meso-scale, where the length-scales are of the same order as the material granularity, plays a key role in controlling material performance and having a quantitative means of characterizing this structure is crucial in developing our understanding of NDE technique signatures of early damage states. High-resolution computed tomography (HRCT) provides an imaging capability which can resolve these structures for many composite materials. Coupling HRCT with three-dimensional physics-based image processing enables quantitative characterization of ...


Implementation Of Automated 3d Defect Detection For Low Signal-To Noise Features In Nde Data, Robert J. Grandin, Joseph N. Gray 2017 Iowa State University

Implementation Of Automated 3d Defect Detection For Low Signal-To Noise Features In Nde Data, Robert J. Grandin, Joseph N. Gray

Robert Grandin

The need for robust defect detection in NDE applications requires the identification of subtle, low-contrast changes in measurement signals usually in very noisy data. Most algorithms rarely perform at the level of a human inspector and often, as data sets are now routinely 10+ Gigabytes, require laborious manual inspection. We present two automated defect segmentation methods, simple threshold and a binomial hypothesis test, and compare effectiveness of these approaches in noisy data with signal to noise ratios at 1:1. The defect-detection ability of our algorithm will be demonstrated on a 3D CT volume, UT C-scan data, magnetic particle images ...


Inversion Of Eddy Current Probe Impedance Data For Crack Reconstruction, John Bowler, D. J. Harrison, S. J. Norton 2017 University of Surrey

Inversion Of Eddy Current Probe Impedance Data For Crack Reconstruction, John Bowler, D. J. Harrison, S. J. Norton

John R. Bowler

The aim of eddy current inversion is to reconstruct an unknown flaw from probe signals measured as a function of probe position and frequency or time. In seeking the solution of an inverse problem, one can take advantage of an ability to solve forward problems by using predictions of probe signals calculated with a tentative estimate of the flaw. A well known inversion strategy adopted here for eddy current inversion, is that of varying the flaw estimate iteratively until the disparity between predicted and observed probe signals is minimized. Then the model flaw which gives the optimum predictions of the ...


Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves 2017 California Polytechnic State University, San Luis Obispo

Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves

Mechanical Engineering

This project is a proof-of-concept ground model of a large deployable antenna designed for the small space requirements of CubeSats. This small deployment module is designed to fit a 2 m by 1 m reflective antenna inside a storage volume of with the dimensions 20 cm by 20 cm x 40 cm. The reflector will be deployed to a parabolic shape with the goal of modeling the reflector necessary for high frequency communication. Because this module is designed as a proof-of-concept for the deployable parabolic reflector specifically, no electrical components will be incorporated and will just focus on the deployment ...


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